Simplify 3d raft or no raft

[Jeremy Rosser]

Just purchased their software using with my makerbot rep 5th gen. Part came out great but raft was a B to get off.

Any tips to adjust raft or setting to not have to use a raft?

Thank you

[Jetguy]

#1 It's a 5th gen with an extruder that has a long melt zone and for whatever reason- uses absurdly high default temps for printing PLA.

As such, we know that combination puts a LOT of heat into the PLA being extruded and that is extremely bad for rafts where we on purpose do not want a good layer bond.

I believe Makerware is either extruding the first layer of the actual object at a lower temp to prevent this extreme bonding or is using a taller than normal layer gap rise such that the first layer of the object has a nozzle height much higher than the actual layer height setting resulting in a poor bond. You can literally watch a makerware print job and see it do these things on the 5th gen. It pauses for a long time after printing the raft waiting for the fans to cool the extruder down.

 

#2 Pros look at rafts as training wheels. I mean it's just insane to me and anyone else experienced in this field- why in the world does the 5th generation- the crème of all knowledge learned after several years of making printers default to using rafts? I'll tell you why- the printer is junk and leveling and Z homing problems mean that first layer height is so variable and so unreliable, the raft is the method of compensation to mask the other major design issues of the printer.

 

#3 You asked a legit question, what can you do?

Decrease the temp of the raft layers, I don't have simplify 3D in front of me, but knowing you can per layer temperature setpoints in the temp tab of the profile.

You can also modify raft settings and try to duplicate how Makerware uses a greater gap for the first layer of the actual object.

 

The problem I really see here is- you bought S3D hoping to fix the very real hardware problems you may or may not have known about the 5th gen and that's a losing battle.

While I love S3D and think it's one of the most powerful slicers around- you simply cannot mask major design flaws and hardware issues with software.

The good news is- once you finally see the writing on the wall and get a different printer- S3D will work with that printer and you'll actually be able to use the "system" to it's fullest and enjoy the hobby.

[JF Kansas]

Model separation from raft is changeable in S3d. You don't have to print the whole model to test it. Just print the raft and the first 10 layers or so. Then see how easy the raft peels off. 

You can also raise the work piece off the build plate about 1.2mm. Then build supports under it and turn dense support layers to 3, 80%, and 1 vertical separation layer. You could also try 60% dense supports and 0 vertical separation layers, this will be harder to remove though. Either way, 1.2mm of support at a .2mm layer height would give you 3 layers of non dense support and 3 layers of dense support.  You can run the supports at a very slow speed in S3D compared to the model and this will allow additional cooling time. Raft speed isn't changeable but not sure if it runs slower than the model settings by default.

This is all theory BTW, as I am a big boy and have outgrown my rafting pants. But it should work if rafting has to be done and you need to alter the settings a little more than the raft settings allow.

[Jeremy Rosser]

I do not want to use rafts either but it give me a consistent bond to the build plate. Do you adjust the z axis or change the first layer height and width to avoid rafts?

I have played with that a little but the bottom of my object does not look as good as when I use a raft.

Thank you for your comments.

[Jetguy]

I only have a shoddy 5th gen Mini and for it, I have to use makerware and go into preferences and adjust the offset.

But note, in order to improve the insanely bad print quality from stock, I installed a stronger return spring in my "not-so-smart extruder" to ensure the nozzle always properly seats in the down position which greatly improves homing and general nozzle precision.

 

If you have poor nozzle return positioning due to the shoddy weak stock spring and bad design, it's highly likely that decreasing the homing gap is reducing the "safety factor" MakerBot built it to keep from ramming the nozzle into the bed. So much so, they actually state that very warning on the adjustment screen.

 

I don't think there is any "magic" you can just adjust in S3D to bypass adjusting the offset in the printer firmware. Just understand- homing is what tells the printer where it is and then print code uses that logical coordinate. 0mm Z represents the homed and physical gap state of Z. I don't know that the firmware will accept negative Z values AKA closer than homed.

[routr71]

Personally, I try to avoid using a raft if possible.  If you're having trouble with parts peeling off of the bed, use a brim.  If you just want to make sure you have a nice consistent thick first layer that will help absorb some of the imperfections of the build plate surface, then just use a thicker first layer in S3D which will act very similarly to a raft.  To do this, disable the raft then go to the Layer tab and increase the first layer height and width until you have the first layer extrusion properties of your choosing.  For example, when I print with my 0.4mm nozzle printer at 0.1mm layer heights, I use a first layer height of 250% and width of 150%, which create a first layer that is 0.25mm thick and 0.6mm wide.  That sticks really well.  You can also adjust the first layer speed if you want to move a bit slower when printing this thicker extrusion.

Another tip that was really useful for my mini is to use the z-axis gcode offset in S3D to make minor adjustments to the nozzle positioning.  This way you can make very fine adjustments to make sure the nozzle is perfectly positioned relative to the build surface

On Wednesday, July 22, 2015 at 9:39:50 AM UTC-4, Jeremy Rosser wrote:

[TobyCWood]

There is a context for when a raft is useful. If the object is positioned such that there are separate support structures that are far enough apart from each other.  A raft can give the whole structure the footing it needs. OTOH with S3D you can build supports that all support each other.

[JF Kansas]

I'd prefer to put a helper disk under the supports instead of using a global raft. 

[Rob R.]

I realize this might be a dead topic at this point, but I've found that using a separate process in S3D for the first layer makes a huge difference for me. I simply adjust that first layer to a greater thickness that helps account for imperfections in the build plate and leads to better adhesion.

I thought I'd mention this since I hadn't seen it in the discussion.

Rob

[tramalot]

yes, but still no rafts....

[Rob R.]

Absolutely agree!

[tramalot]

s3d is not a raft place, NEVER USE A RAFT 

On Wednesday, July 22, 2015 at 9:39:50 AM UTC-4, Jeremy Rosser wrote:

[TobyCWood]

You can do that without a separate process... However using separate processes is a good thing because you learn how to do it and then all of a sudden you see tons of possibilities.